Polarisation effects of second-class currents in the direct and inverse β decay of nuclei

A general expression for the modulus squared of matrix elements of semileptonic weak processes including the polarisation of the initial (final) nucleus is obtained. The influence of second-class currents (SCC) on various characteristics (the charge asymmetry, the angular and spin correlation coefficients, etc) of the beta decay of 12B, 12N and 6He and of the iso-elastic scattering of nu ( nu ) on 12C is studied. It is shown that experiments with a polarised nucleus will allow new effects, induced by SCC, to be extracted. An optimum geometrical configuration of the test for conducting experiments to observe these effects is found.